Traditional motion-sensing products use passive infrared (PIR) sensors to recognize moving heat sources, such as people, animals, or car engines. PIR sensors have been the standard technology used in outdoor motion-sensing products for years, and the effectiveness of PIR sensors is typically determined by the design of the motion-sensing apparatus, the quality of the components used in making the motion sensing apparatus, and the current weather conditions. Rain, and wind-blown leaves and branches cause false positives, or false tripping, of a typical PIR motion sensor. Further, the typical PIR motion sensor performs differently in heat than it does in cold. Therefore, depending on where a user lives geographically, climate can have an effect on the performance of the PIR motion sensor and accordingly the fixture. In cold climates people are generally wearing insulated coats. The outer surface of the coat can be a similar temperature to the surrounding environment, thereby making it difficult to detect a person's motion. On the other hand, in warm climates, a person body temperature while walking across a paved driveway may be the same temperature or substantially close to the same temperature as the pavement, thereby making it difficult for the PIR sensors to detect motion.
Another problem with conventional motion sensors is that a person can walk straight towards the conventional PIR-based motion sensor and the motion sensor will not detect motion until the motion is occurring immediately in front of the sensor. This is due to the radial detection zones that are relied upon by the PIR sensor's lens optics. These radial detection zones extend out from the center of the sensor into the detection area and only allow motion to be detected by the sensor when a temperature change is found in one of the zones. For example, if a person walks directly toward the sensor and does not move from one zone to the next, the person will not be detected because the temperature remains the same in that zone. As the person gets closer to the sensor the zone gets smaller and smaller until it is impossible to keep from crossing to the next zone.
Further, the present invention overcomes the problems associated with merely moving standard Doppler radar, that may be used in an indoor environment, to an outdoor environment. For example, if a typical indoor Doppler radar system is used in an outdoor application, without the benefit of the present invention, the system will detect motion of any object moving towards the unit, including dirt, leaves, bugs, and the like, resulting in wanted and unwanted motion detection. Leaves or other objects blowing around will cause a typical indoor Doppler radar system to activate. Detecting this type of motion is considered a “false tripping” condition for an outdoor motion detector and would be objectionable to the consumer because, for example, a light would be activated in the middle of the night even though no person is in the area.
The present invention overcomes these problems caused by environmental weather conditions that either cause “false tripping” or “no-tripping” conditions in traditional motion sensors through the addition of a Doppler radar, which can make a decision about whether motion has been detected based on information provided by the Doppler radar sensor or a combination of information provided by the Doppler radar sensor and the PIR sensors.